Field of the Invention
The present invention relates to a method of producing a liquid developer for use in image-forming apparatuses that utilize an electrophotographic system, e.g., electrophotography, electrostatic recording, and electrostatic printing. The present invention also relates to the liquid developer produced by this production method.
Description of the Related Art
The need for color capabilities in image-forming apparatuses that utilize electrophotographic systems, for example, copiers, facsimile machines, and printers, has been on the increase in recent years. Within this context, the development is being actively pursued of high image-quality high-speed digital printers that utilize electrophotographic technologies that use liquid developers, which have an excellent reproducibility for fine line images, an excellent gradation reproducibility, and an excellent color reproducibility and which are excellent for high-speed image formation. Given these circumstances, the development is required of liquid developers having better properties.
A dispersion of colored resin particles in an insulating liquid, e.g., a hydrocarbon organic solvent or silicone oil, is already known as a liquid developer. However, when, in the case of such a liquid developer, the insulating liquid remains present on the recording medium, e.g., paper or plastic film, this ends up causing a substantial deterioration in the appearance of the image, and due to this the insulating liquid must be removed. In a method generally used to remove the insulating liquid, thermal energy is applied to volatilize and remove the insulating liquid; however, this is not necessarily preferred from an environmental perspective, for example, a vapor of the volatile organic solvent ends up being emitted from the apparatus and large amounts of energy are consumed.
A method in which the cure of a reactive functional group-bearing insulating liquid (Japanese Patent No. 3,442,406) is brought about has been disclosed as a countermeasure to the preceding. This method, which uses a reactive functional group-bearing monomer or oligomer as a curable insulating liquid, can form images using less energy than thermal fixing systems, which require the volatilization and removal of the insulating liquid through the application of thermal energy. Methods based on wet pulverization methods have been disclosed as methods for producing this liquid developer. However, these methods have required the execution of a time-consuming wet pulverization treatment in order to reach the desired particle diameter and have been encumbered by the problems of requiring long periods of time for production and of a substantial reduction in the production efficiency.
A method of producing a curable liquid developer using a chemical procedure (Japanese Patent No. 5,277,800) has also been disclosed. However, this method requires substitution to the insulating liquid by drying the particles after toner particle formation has been carried out in water on an interim basis, and due to this the number of steps in the production process has been increased and the use of large amounts of energy has been required for production and this method has been encumbered by a substantial reduction in the production efficiency.